The invention concerns an apparatus for the production of container jackets from flat blanks of cardboard or plastic.
An apparatus of this type is known (for example, see German Pat. No. 27 43 838), wherein a strip-like sealing head is provided which is pressed by a pneumatic cylinder against the overlapping area of a blank wound around a core. With such an arrangement, it is not always possible to align the contact pressure strip (serving as the sealing head) along a line parallel to the axis of the core, in order to obtain a contact pressure defined in all of the area. The possibility exists of displacing the strip by means of a rocker, but even then there is no assurance of an accurate alignment of the contact strip.
Other types of such machinery (e.g., cup machines of the Michael Horauf Co., West Germany) have a support for the contact strip which permit only movements radially to the axis of the winding core. The contact pressure is also applied by means of such support, which in actual practice is mounted under the winding core. That arrangement is chosen because the winding cores are components of a rotating table and therefore both the support and the drive elements are located in the vicinity of the rotating center of the rotating table radially inside of the winding cores, in order to keep the inertia forces low and for reasons of space. The fact that in such an arrangement the contact strip is loaded asymmetrically adversely affects the quality of the joint in the overlapped area of the blank.
Even if the afore-described mechanisms are configured to apply a uniform contact pressure along the length of the overlapped area for a given jacket structure, it is not possible to adjust the mechanism to continue applying a symmetrical pressure in the event of certain changes in the jacket format, such as a change in the longitudinal length of the jackets.
It is, therefore, an object of the invention to provide an apparatus of the afore-mentioned type such that, while retaining accurate guidance, it will be possible to apply force symmetrically to the contact strip even in the case of container jackets of different formats.
This object is attained by the present invention which comprises a winding core around which a blank is wound in a manner forming an overlapped area. A pressing element is arranged to engage and press the overlapped area along a length of that area parallel to a longitudinal axis of the jacket. An actuating mechanism urges the pressing element against the overlapped area in a radial direction with reference to the axis to apply a pattern of radial pressing forces along the length of the overlapped area. The actuating mechanism is able to longitudinally shift the pressing force pattern along the overlapped area to adapt the apparatus to the pressing of different types of jackets.
By means of this arrangement, the contact pressure may always be applied to the overlapped area. The point of pressure application may be displaced to conform to different jacket lengths, whereby a symmetrical application of pressure is always assured.
The pressing element is activated by means of a rocker arm which facilitates mounting of the apparatus into the area of the winding star. By varying the point of articulation of a pressure lever on a yoke holding the pressing element, the point of the application of the force may be shifted longitudinally in a very simple manner.